1. Field of the Invention
An aspect of this disclosure relates to an image forming apparatus, an image forming method, and a storage medium storing a program for causing a computer to perform the image forming method.
2. Description of the Related Art
In a typical electrophotographic image forming apparatus, an electrostatic latent image is formed using a laser beam on a photosensitive drum and the electrostatic latent image is developed with toner to form a toner image. The toner image is transferred onto paper and fused onto the paper by applying heat and pressure to form a stable image on the paper.
In the above process, misalignment between the paper and the formed image (or an error in the position of the formed image on the paper) may occur due to, for example, slippage between the paper and a paper conveying unit or slippage between sheets of paper. Japanese Patent No. 4280894, for example, discloses a technology for preventing the misalignment between paper and a formed image.
In a configuration disclosed in Japanese Patent No. 4280894, the leading edge of paper is detected with a sensor to determine paper-feed timing and a drive motor for driving a paper conveying unit is controlled based on the determined paper-feed timing such that transfer of a toner image from a photosensitive drum to the paper is started from a predetermined position on the paper.
With the configuration of Japanese Patent No. 4280894, it is necessary to prepare a target driving profile indicating timing and other parameters for driving the drive motor. FIG. 1 shows an exemplary target driving profile. In FIG. 1, the horizontal axis indicates time, the left vertical axis indicates a target speed, and the right vertical axis indicates a target position.
However, the timing difference between an image and paper (i.e., the difference in the feed timing of the image and the paper) differs from one image forming process to another, particularly when different types of paper are used. Also, in a high-quality image forming apparatus, it is necessary to correct the timing difference between the image and the paper at every transfer step. Therefore, in such a high-quality image forming apparatus, it is necessary to generate a target driving profile each time after the feed timing of the image and the paper is detected.
The target driving profile may be generated based on a look-up table. However, this approach makes it necessary to provide a large amount of memory for storing the look-up table and to increase the computing power of a processing unit to generate the target driving profile. This in turn increases the costs of an image forming apparatus.